Fine needle aspiration (FNA) has been a well accepted method for obtaining tissue samples for pathologic or histologic analysis in diagnosing tumors of the pancreas and other soft tissue organs. Endoscopic ultrasound (EUS) and EUS-guided fine needle aspiration (EUS-FNA) have become important tools in the evaluation of pancreatic masses.
Conventional surgical techniques for obtaining tissue samples accessible only through a flexible ultrasound-endoscope using a fine needle generally require numerous needle sticks. These procedures often result in obtaining a small number of cells with each aspiration, cells which may or may not be diagnostic. In addition, such procedures are often traumatic because of the multiple needle passes that it necessitates. This is especially true in the case of pancreatic biopsies. The pancreas secretes digestive enzymes. When injured, these enzymes are released, and may induce self digestion, and necrosis of the pancreas, and adjacent organs. The current technique used during Endoscopic Ultrasound Fine Needle Aspiration (EUS-FNA) of a pancreatic tumor entails the passage of an 18-22 gauge stainless steel needle. This needle is passed through the working channel of a linear echo endoscope under real-time guidance into the endo-sonographically visualized pancreatic mass. The needle is moved back and forth multiple times through the lesion with varying degrees of suction applied to it. The specimens obtained are then deposited onto a cytology slide for immediate fixation, staining and cytopathologic examination.
Aspirating a sample from a fluid medium through a needle is a simple procedure. Aspirating a sample from a solid mass is difficult. Most pancreatic EUS-FNA procedures take up to 30 needle passes to make a definitive cytological diagnosis of pancreatic carcinoma. Oftentimes, the only cells that are obtained are blood cells, or normal pancreatic tissue cells. Even when tumor cells are captured, these are often fragmented, and separated from each other. It is therefore almost impossible to differentiate a primary pancreatic tumor from a metastatic lesion.
Despite the time consuming and traumatic nature of the current FNA procedure, the consequence of a non-diagnostic aspirate is worse, because a missed diagnosis of pancreatic cancer is a sure death sentence. Therefore, if a pancreatic tumor is suspected but the FNA result is negative, the patient must then undergo a pancreatic biopsy through an abdominal incision. Although needles for taking core biopsies of internal organs exist, these needles are much thicker than the needles used during fine tissue aspiration. An example of such a needle is the Mangini needle, with which percutanious liver biopsies are used. In order to introduce this needle into the liver, an incision must be made in the skin with the sharp tip of a scalpel. The needle is then pushed into the incision, and under aspiration is quickly pushed in and out of the liver with a quick stabbing motion. The resulting core biopsy is almost always diagnostic, and ample to examine sheets of tissue cells representative of the pathology that is sought. The injury, however, is much greater than that inflicted with a fine needle.
The choices for obtaining diagnostic tissue from internal organs are three fold. The first choice is to obtain a biopsy though an open operative incision or a laparoscopic technique, which entails surgical intervention. The second option is to use a large diameter stiff stainless steel needle. This method may only be used for lesions that are near the exterior of the body, such as described above in relation to the Mangini needle. The third method is to obtain cells through a fine needle with ultrasound guidance. While this method is least traumatic with only one needle introduction, it produces a poor yield of diagnostic material. In the best case scenario, and after multiple needle sticks, several cells of the tumor are retrieved. Because the cells are obtained separate from one another, they are examined by the pathologist without their spatial relationship to the rest of the organ that they originated from. In the worst case, even these tumor cells are not obtained, only blood cells and normal tissue, necessitating one of the more invasive procedures. It is therefore most desirable to have an instrument of being passed through the flexible endoscope that is both delicate so as not to traumatize the area that is being biopsied, and at the same time be capable of obtaining a core tissue biopsy that will be diagnostic. It would be of great advantage if diagnostic certainty could be achieved with a minimal number of instrument passes, thus achieving excellent results with minimal trauma to the patient.
The fine needle aspiration technique is also widely used to obtain cells from suspected lesions in organs that are more superficial. These organs include breast, prostate, thyroid and parathyroid. Although these organs are more accessible to the needle than the pancreas, the trauma incurred by a thick core biopsy needle stick is great. Millions of women undergo fine needle aspirations for suspected breast cancer. Here too, 10-15 needle sticks are required to obtain what is deemed a sufficient number of cells for an adequate specimen.
When a woman comes for such a biopsy, she is anxious and afraid of the impending diagnosis. Oftentimes she leaves the procedure with a large hematoma, an internal blood-clot in a severely bruised breast, resulting from the numerous needle sticks required to obtain cells. Recently, a biopsy gun has been introduced for this purpose. The gun is equipped with a thicker needle, spring loaded to jump out of the instrument, and into the suspected lesion. This method has rendered many women even more anxious. A short, inflexible fine needle, one of the same diameter as the fine needle currently used for aspiration, would be of great benefit if it would enable a single needle pass into an organ such as the breast, and obtain a core biopsy on one relatively atraumatic needle pass.